Information storage devices are in wide spread use, and are used to store and retrieve large amounts of data. Such information storage devices generally include a rigid media for storing information, a read/write device for creating and accessing the information, and an actuator assembly for positioning the read/write device over the rigid media. One common example of such an information storage device is a hard disk drive having one or more rotating magnetic disks, over a surface of each of which a head suspension and a head slider are positioned. Each of the head suspensions is attached to an actuator arm of the actuator assembly, and the actuator assembly thus positions the suspensions and sliders at a desired location over the rotating disks.
A conventional actuator assembly in a hard disk drive includes an actuator block, one or more arms extending from the actuator block, and a plurality of head suspensions that are mounted to the arms of the actuator block. The actuator block and arms extending from the block are typically machined from a single piece of starting material, such as aluminum, and are typically referred to as an E-block. The number of arms on the E-block and the number of head suspensions in the actuator assembly are usually dependent on the number of disks in the disk drive, with a head suspension positioned over each magnetic surface of the individual disks. Each head suspension is typically mounted to an arm of the E-block by swaging or ball staking a vertical swage boss extending from a base plate on an end of the head suspension to the arm. In this method, the swage boss is inserted in a hole in the arm and is then deformed to engage the arm by forcing a round ball through the boss. The E-block is coupled to a rotary actuator within the disk drive, and in this manner, the head suspensions can be positioned over a desired location of the disks.
E-blocks having suspensions mounted to the arms of the block have certain disadvantages, however. Increased spacing between the suspensions is typically required to accommodate the height of the vertical swage boss. In addition, a large vertical force must be used to swage the boss to the actuator arm, which can warp or otherwise permanently deform the actuator assembly. Suspensions that are swaged to the actuator block also cannot easily be selectively reworked or replaced due to the nature of the swaging process.
In recent years, integral arms comprising an actuator arm and a head suspension have been introduced into the disk drive industry to address these disadvantages. In such an embodiment, a head suspension is formed integral with an actuator arm from a single piece of material, and the integral arm is mounted to an actuator spindle, such as for example by inserting the spindle through an aperture at a proximal end of the integral arm. The spindle is coupled to an actuator, and the actuator positions the integral arm over a desired location of a disk. Because the suspension is formed integral with the actuator arm, an integral arm does not require additional spacing for a swage boss tower, and the arm is not deformed by the large forces required to swage the suspension to the arm. An integral arm also typically has less mass and inertia than an E-block/head suspension combination, which can increase the response time for positioning the head suspension over the disk.
Actuator assemblies can be formed having a stacked array of integral arms to access data stored on a plurality of disks within an information storage device. In such a stacked array, a spindle is inserted through the aperture of a bottom integral arm, and a spacer is placed over the spindle. A stacked array can be formed by placing the aperture of a second arm over the spindle, and a third arm can be placed back-to-back with the second arm in a similar fashion. A spacer can be inserted between the second and third arms if desired, and additional arms and spacers can be added to the spindle as necessary for a specific application. After the desired number of arms are inserted over the spindle, a washer and lock nut can be placed on the spindle and tightened to provide an axial compressive force that frictionally secures the arms and spacers to the actuator spindle.
One shortcoming of an actuator assembly having such a stacked array is that, should one or more of the head suspensions on the arms fail, it is cumbersome to replace the arm having the failed suspension. That is, unless the failed arm is at the very top of the stacked array, the array must be disassembled down to the level of the failed arm, the arm replaced, and then the stacked array reassembled by inserting the arms and spacers over the actuator spindle, and then re-engaging the washer and lock nut to secure the arms and spacers.
Attempts have been made to allow individual arm/suspension combinations to be replaced without disassembling an entire stacked array through the use of spring arm mounts between the arms and the actuator spindle of an actuator assembly. For example, in U.S. Pat. No. 5,631,789, issued May 20, 1997 to Dion et al., a pair of spring-like fingers of an actuator arm are used to clamp the arm to the housing of a bearing assembly. The housing of the bearing assembly is machined to have an annular groove that receives the spring-like arms of an individual actuator arm.
The attachment structure of the '789 reference, however, suffers certain shortcomings. For example, while it is possible to selectively rework an individual actuator arm having a head suspension attached thereto without disassembling the stacked array, it can be difficult to grasp the individual actuator arm due to the relatively close spacing between arms, and damage to surrounding arms and/or suspensions can result. This problem is exacerbated by the general industry trend toward smaller storage devices, which further reduces the room between individual arms and suspensions, making it more difficult to grasp the arms.
Moreover, it is important that the individual arms of the actuator assembly be positioned at the appropriate height (commonly referred to as the Z-height) above an associated disk in the information storage device. In this regard, the arms must be mounted to the actuator spindle at the appropriate location. The location of the arms on the spindle is driven by the position of the grooves that are engaged by the spring arms of the arm/suspension combinations. Manufacturing tolerances on the machining of the grooves can, however, introduce errors into the Z-height of the arm/suspension components.
There is therefore a continuing need for an actuator assembly having a mount for individual head suspensions. Such an improved assembly should securely hold head suspensions in place as the actuator rotates, and should permit the selective rework or replacement of head suspensions, while reducing the potential for damage to other head suspensions in a stacked array. An actuator assembly that provides accurate Z-height spacing of the head suspensions while also reducing the spacing between individual head suspensions would also be highly desirable.